As long as the "central" location is calculated as a weighted distance to interesting/challenging/scenic/and world-class offroading.
Socal is just about balanced by Colorado, so the epicenter in my humble opinion would be Moab or Grand Staircase-Escalante, UT. Too much of the east of the rockies is uninteresting, really, and the terrain is duplicated elsewhere. No offense meant to the east, but it's just older, and I grew up there, and already saw most of the historical places from Chicago to the Atlantic.
Regional meets make a LOT more sense. And they get exponentially tougher to put together the more folks you have.
Personally, if I'm working and can afford the fees, I'd rather just have a bunch of us meet at the next Overland Expo.
http://www.ovexpo.com/Home.html Mid-April, 2010 in Southern Arizona. $255 single/$465 family - per vehicle.